Metal products formed in complicated shapes are often produced by casting. Casting is a production process in which metal having fluidity (molten metal) is solidified in a desired shape to obtain a target casting. It is technical common knowledge long believed that a casting mould having a cavity suitable for a desired shape of a target casting is an indispensable device for casting. Therefore, the casting methods conventionally employed often led to a variety of problems caused by using the casting moulds. The problems are, for example, casting defects (solidification cracking, shrinkage porosity, gas blow holes, etc.), ununiformity of solidified structure, deterioration of material yield, environmental burden, or the like. A number of technical approaches have been proposed to solve each of the conventional problems from a microscopic point of view.
Apart from these technical approaches, some technical solutions were disclosed, which address the problems differently from the conventional casting methods in which casting moulds are used. The patent literatures which recite examples of such a casting technique are listed below.